A riddle, wrapped in a mystery, inside an enigma…

If you find the news from inside Iran somewhat bewildering, and if you don’t know whether to believe those who think the clerical regime is on its last legs or those who think it will easily contain the opposition, don’t feel bad. The reality is that nobody — including the leaders of the Iranian government, ...

If you find the news from inside Iran somewhat bewildering, and if you don’t know whether to believe those who think the clerical regime is on its last legs or those who think it will easily contain the opposition, don’t feel bad. The reality is that nobody — including the leaders of the Iranian government, the opposition, and all of us watching from outside — knows where they are headed or what the timetable for change might be. We’ll know who guessed (yes, guessed) right some weeks, months, years, or decades from now, but right now trying to handicap events there is a mug’s game. Here’s why:

First, we don’t have very reliable information coming from inside Iran itself, partly because the regime is doing its best to limit it. That’s not to say that we have no information — in the form of emails, journalists’ accounts, twitter feeds, viral videos, and even some surveys of public opinion — the problem is that it is very hard to know how representative it is, what the larger context is, or what any of it actually means.

Second, the information we do have is tainted by what economist Timur Kuran termed "preference falsification." An individual’s true beliefs are a form of private information, and there’s no way of knowing whether someone who is expressing support for the regime is revealing their true beliefs or not. Even a large anti-government rally doesn’t reveal very much about what the people who stayed home are thinking, or how participants or bystanders would react in the event of either a crackdown or concessions by the ruling party. You might be willing to demonstrate if you think it’s safe to do so, but your anti-regime feelings might not be so intense that you’re willing to take big risks to express them. If enough Iranians feel this way, then the regime is probably safe; the key is that it is essentially impossible to figure this out ex ante.

Third, commentary and testimony about these events is invariably biased by the goals of the various interested parties. Iranian officials will naturally try to convince us (and the Iranian public) that most of the country backs them and that the opposition forces are in cahoots with us, with Israel, and other outside forces. By contrast, the Green movement wants to convince the outside world (and neutral Iranians) that their support is broad and growing. Not surprisingly, Iranian exiles in Europe and America — most of whom detest the regime — have obvious incentives portray it as fragile and are therefore likely to exaggerate the power of the opposition. This is an old story: all revolutions generate an exile population that is eager for revenge and restoration and looking for foreign support, and the Iranian revolution of 1980 is no exception. And then there all those other people who are eager for regime change and alarmed by Iran’s nuclear program, and who have an obvious incentive to see the disturbances as an opportunity to squeeze the regime a bit more.

In short, we are dealing with a situation where information is scarce, biased, and likely to be interpreted for us in various self-serving ways. In light of this unavoidable uncertainty, the smart bet is still to assume the regime will hang on and base U.S. policy on that assumption, while remaining alert for signs that the assumption is incorrect. Why? Because “hanging on” is what usually happens. Authoritarian regimes have many ways of clinging to power, and even very unpopular governments often prove to be surprisingly durable. The Soviet empire faced revolts in East Germany in 1953, Hungary in 1956, Czechoslovakia in 1968, and Poland in 1980, and it staggered on until 1989. Moreover, it took a new leader chosen by normal procedures (Gorbachev) to begin the revolutionary process. One could say the same for the failed Russian revolution of 1905 or still-born revolutions in Europe in 1848; in both cases governments tottered but did not fall. Big revolutions are relatively rare events, and the precise timing usually takes most observers by surprise, for the reasons noted above.

I also believe that using military force against Iran would be a mistake and that tougher economic sanctions aren’t going to hasten the regime’s demise. In terms of U.S. policy, therefore, the best course remains “engagement without illusions” where the short-term goal remains persuading the regime not to acquire nuclear weapons and the long-term goal is to allow political processes within Iran to erode the regime from within. The only way to achieve the former is to give up on getting Iran to forego all enrichment, and instead allow them limited enrichment provided they ratify and implement the Additional Protocol of the NPT. The best way to achieve the latter is to let Ahmadinejad & Co. do the raving, and not give him any ammunition by indulging in a lot of saber rattling ourselves. We should continue to reiterate our belief that the Iranian people should be allowed determine their own fate, but take no steps that suggest we are trying to dictate that fate ourselves.

I continue to fear that we are exaggerating the likelihood of regime change in Iran and exaggerating the strategic benefits it will bring. In other words, we may be falling prey to a lot of wishful thinking, and that’s usually not a good basis for sound policy.

Stephen M. Walt is the Robert and Renée Belfer professor of international relations at Harvard University.